Adhesion molecules participate in adhesion between cells and cells, and between cells and cell matrix. Adhesion molecules include a number of families such as integrin family and immunoglobulin super family. The adhesion molecules belonging to integrin family are those expressed on leukocytes such as lymphocytes, monocytes, basophils and eosinophils. These adhesion molecules have heterodimer structure, in which an a chain and a β chain are non-covalently bound, and are classified into some subfamilies depending on the species of the β chain. VLA-4 (very late antigen-4) also called α4β1 or CD49d/CD29, a member of the integrin family, participates in the interactions between leukocytes and vascular endothelial cells or extracellular matrix, and participates in infiltration of leukocytes into inflammatory site. VCAM-1 (vascular cell adhesion molecule-1) and fibronectin are known as the adhesion molecules which interact with VLA-4.
The binding site on fibronectin, which binds to VLA-4 is a fibronectin fragment called CS-1. It has been reported that the minimum unit required for the binding in this fragment consists of 3 amino acid residues, that is, Leucine-Aspartic acid-Valine.
Linear or cyclic peptidic VLA-4 adhesion inhibitor compounds based on the 3 amino acid residues, Leucine-Aspartic acid-Valine have been reported (WO/15973).
On the other hand, it is known that the expression level of VCAM-1 which is another adhesion molecule that also interacts with VLA-4, is increased by stimulation by a cytokine such as IL-1, TNF-α or IL-4, and that VCAM-1 interacts with VLA-4 existing on cells such as lymphocytes, NK cells, monocytes and eosinophils. VLA-4 and VCAM-1 participate in the infiltration of leukocytes into inflammatory sites through blood vessels. From this view point, the interaction between VLA-4 and VCAM-1 is very important in inflammatory reaction.
Among the adhesion molecules, VCAM-1 belongs to the immunoglobulin super family, and 7-Ig-like-domain VCAM-1 and 6-Ig-like-domain VCAM-1 are known. Mutation experiments of VCAM-1 revealed that the binding sites on VCAM-1 for binding to VLA-4 are located in domain 1 and domain 4, and that the amino acid sequence of glutamine-isoleucine-aspartic acid-serine-proline on the CD loop is important for the binding to VLA-4 (e.g., J. Cell Biol., 124, 601(1994)). J. H. WANG et al. reported a cyclic peptide Cys*GlnIleAspSerProCys* (Cys*Cys* represents disulfide bond) which has an inhibitory activity against adhesion of VLA-4, which cyclic peptide is based on the glutamine-isoleucine-aspartic acid-serine-proline (Proc. Natl. Acad. Sci. USA, 92, 5714 (1995)). Low molecular compounds having VLA-4-inhibitory activity have also been reported (e.g., U.S. Pat. No. 5,770,573, U.S. Pat. No. 5,821,231 and WO99/6436).
The fact that VLA-4 plays an important role in inflammatory reaction has been proved by experiments using anti-VLA-4 antibody in animal models such as contact hypersensitivity, delayed type hypersensitivity models (mouse and rat), experimental autoimmune encephalomyelitis models (mouse and rat), nephrotic nephritis (rat), passive cutaneous anaphylaxis model (guinea pig), immunocomplex-induced pulmonary injury model (rat), spontaneous colitis model (monkey), asthma model (sheep) and adjuvant arthritis model.